Pumping system



Feb. 24,l 1942. H, F vlcKERs 2,274,224

` PUMPING SYSTEM Filed July 24, 1940 INVENTOR HARRY F. VIQKERS ATTORNEY Patented Feb. 24, 1942 PUMPING SYSTEM Harry F. Vickers, Detroit, Mich., assignor to Vickers Incorporated, Detroit, Mich., a corporation of Michigan Application July 24, 1940, Serial No. 347,240

I (Cl. 103-49) 3 Claims.

This invention relates to power transmissions, particularly to those of the type comprising two or more uid pressure energy translating devices oneof which may function as a pump and another as a fluid motor.

The invention is more particularly concerned with a liquid fuel pumping system for use with internal combustion engines. In many engine installations, particularly those on aircraft, the fuel supply tanks are located at a considerable distance from the engines and below the level thereof, and, where highly volatile fuels are used, vapor-lock trouble is frequently encountered with systems in which the fuel pumping means is 1ocated adjacent the entrance and must draw fuel from the tank by suction through a long suction conduit. The vapor-lock diiiiculties may be avoided by placing the pump close to or in the tank, but this complicates the problem of transmitting power from the remotely located engine to the pump.

It is an object of the present invention to provide an improved fuel supply system adapted for installations of this character wherein the pump may be located closely adjacent to the tank and may be operated from the engine by hydraulic transmission of power.

More particularly, it is an object of the invention to provide an improved fuel supply system having a pair of independently operable pumpv ing elements, each of which is normally biased by a substantially constant force to deliver fuel into the delivery line, together with intimately operable hydraulic means for retracting the pumping element of each pump individually.

It is a `further object to provide in an apparatus of this character a control system for the hydraulic operating means which is automatically controlled by movement of the pumping elements and which provides a more rapid retraction stroke than the pumping stroke under all normal conditions and which further insures that the pumping strokes of the two pumping elements will overlap in point of time so that at all times at least one of the pumping elements will be effective to deliver fuel.

Further objects and advantages of the present invention will be apparent from'the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

The single figure is a diagrammatic view of a fuel supply system incorporating a preferred form of the present invention.

Such a. system may comprise a pair of individual pumping elements comprising cylinders 2 and 4 within which pistons 6 and 8 are reciprocablyl mounted. Rods I6 and I2 extend through the bottom end caps I4 and I6 to form operating means for the respective pistons. There is thus provided a pair of differential-area cylinders constituting the fuel pumping elements. Fuel may be conducted to the pumping elements from the tank by a short line I8 which extends through inlet check valves 20 and 22 to the upper or large end of the cylinders 2 and 4. Outlet check valves 24 and 26 permit outflow from theupper end of the cylinders to a fuel supply conduit 28. The inlet conduit I8 also connects through check valves 32 and 34 with the small end of cylinders 2 and 4. A bypass conduit 3| of large capacity extends from the small end of cylinder 2 to the large end thereof through a check valve 33. As an equivalent arrangement for cylinder 4, the piston 6 is shown as provided with two or more check valves 35 therein.

For the purpose of operating the pumping pistons 6 and 8, a pair of fluid motors are provided beneath the pumping cylinders. These may comprise a pair of cylinders 36 and 38 having pistons 46 and 42 therein. The latter are connected to the piston rods I0 and I2 and have tail rods 44 and 46 of larger diameter extending through the bottom ends of the cylinders 36 and 38.

The pistons 6 and 8 are each biased upwardly by a spring 48 and 50 and also by hydraulic pressure constantly exerted over the small area at the bottom of pistons 4I)` and 42,. For this purpose pressure fluid is conducted from a source of constantpressure, such as an accumulator system, generally designated as 52, by means of a conduit 54 to a valve block 56 which forms part of the bottom end closure member for the cylinders 36 and 38. The conduit 54 communicates with a passage 58 having branches 66 and 62 extending to the bottom end of the cylinders 36 and 38.

Fluid may be admitted alternately to the upper ends of the cylinders from the pressure source 52 under the control of a shiftable four-way valve 64. The spool 66 of the valve isv adapted to be shifted to the left or right by means of a rod 68 having an over-center linkage connection 10 with the spool 66. The latter is of the type which permits the rod 68 to shift almost to its extreme positionbefore the spool66 begins to shift. The valve 64 is of the customary four-way type and has a pressure port 1I in communication with theA supply conduit 64. The valve also has a return port 12 which communicates by means oi a conduit 1I with a suitable reservoir. On opposite sides of the pressure port 1| there is provided a pair of cylinder ports 1I and 18 while a similar pair of cylinder ports 18 and 88 are provided on opposite sides of the return port 12. Ports 18 and 18 are connected together by a duct 82 and communicate with the upper end of cylinder 36 through a passage 84. Likewise ports 14 and 88 are connected together by a duct 88 and communicate with the upper end oi' cylinder 38 by a passage 88.

For the purpose of shifting the rod 88 and the valve 68, the former is provided with rollers 80 and 82 on its opposite ends which are adapted to contact withl cams 84 and 88 carried by the tail rods Il and 48.

In operation, assuming the parts to lie in the position illustrated, it will be seen that pressure iluid is admitted through conduit 54, conduit 68,

port 1| and branches 88 and 82 to the lower end of both cylinders 86 and 38. This together with a portion of the springs 48 and 60 exerts a suba substantially constant pressure on the fuel in its upward movement. Fluid discharged from the lower endof cylinder 38 flows outwardly to branch 88 and duct 58 to join with the incoming fluid from pipe M thus increasing the speed of downward movement.

As soon as the upper end of cylinder 38 was connected to the return conduit by the opening up of port 88 to port 12, the piston' 8 started moving upwardly under its constant bias and took over the duty of delivering fuel to the discharge conduit 28. v This upward movement continues until the cam 86 shifts the rod 68 to the left again thus restoring the spool 66 and rod 88 to the position shown on the drawing and again permitting the piston 8 to move upwardly. During the shifting of the spool 68 there was, of course, the same interval during which both pistons were relieved of downward pressure on their respectiveheads thus insuring that there is no instant during which at least one piston is free to exert its constant pressure on the fuel in the supply line.

It will be noted that during the downward movement of either piston the fuel in the lower .end of the cylinder 2 or l, as the case may be, is

discharged out through the conduit 3| and check l valve 33 or through check vales 35 to the head discharge line 28 moving upwardly to discharge fuel as fast as it is consumed at the far end of the line 28. At the same time fuel is drawn into the lower end of cylinder 2 from the fuel supply conduit |8 through the check valve 32 and conduit 3|. Normally the upward movement of v either piston takes place at a relatively slow speed so that the same size conduit at the inlet and outlet lines of the cylinder 2 permits unrestricted flow to and from the two ends of the cylinder.

It will be noted that the cam Min the position of the piston 8 shown in the drawing has already started to move the rod 68 to the right but not far enough to cause the over-center mechanism to shift the spool 88. Preferably the curvature of the cam 84 may be such that the mechanical advantage between tall rod 4I and shifter rod 88 progressively decreases in the same proportion that the force required to shift the over-center mechanism decreases. Thus a constant force will be exerted on the tail rod M by the roller 88. As the piston 8 moves upwardly a 1 predetermined farther distance. the rod 68 is shifted rightwardly to the point where the overcenter mechanism snaps shifting the valve 68 also to the right.

It will be noted that dueto the different lengths of the two grooves in the valve spool cooperating with the ports 1| and 12 that the supply pressure will .be cut olf from the cylinder 38 before it is opened to cylinder 36. On the other hand, at port 'I2 the cylinder 36 is not cut oi from the return line until after cylinder 38 has been opened up thereto. Thus there is an appreciable interval while both pistons are free to move upwardly under their constant bias.

As the spool 68 continues its movement to the right the port 16 is openedto the port 1|, and pressure fluid is thus admitted to the upper end of cylinder 36. Due to the larger area at the top of piston 40, this pressure fluid overcomes the bias on the piston and moves the latter downwardly at a relatively rapid rate compared with end of its respective cylinder. In this way the more rapid movement of the'piston on its suction stroke is permitted to occur without substantially increasing the rate of flow through the suction conduit i8. In other words, on the slow upward stroke of each piston it fills the chamber at the lower end of thel cylinder, and during the rapid retraction stroke this volume is utilized to help fill the upper end of the cylinder by direct transfer from one end to the other through the inlet valve 20 or 22, as the case may be. The quantity thus transferred is, of course, not quite suicient to ll the upper cylinder chambers, due to the smaller area of the lower cylinder chambers. The dilerence required, however, may be drawn from the suction line i8 through the inlet check valves 20 and 22 without creating excessive suction in the line I8.

While the form of embodiment. of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow."

What is claimed is as follows:

1. In a fuel supply system for an internal combustion engine the combination of a pair of expansible chamber pumps having valved connection with a source of fuel and with a fuel delivery conduit, a source of hydraulic power fluid, independent uid motors for operating said expansible chamber pumps on their intake strokes, biasing means for operating said pumps on their outlet strokes to exert a substantially constant pressure on the fuel delivery lineindependently of the rate of fuel consumption, and valve means operated by each fluid motor near the end of its pumping strokefor first relieving pressure in the other motor to start the latter on a pumping stroke and later admitting pressure to the former motor to start it on an intake stroke.

2. In a fuel supply system for an internal combustion engine the combination of a pair of expansible chamber pumps having valved connection with a source of fuel and with a fuel delivery conduit, means biasing said pumps in the direction of a pumping stroke, and hydraulically operated means for alternately retractlng said pumps on a suction stroke. said last means including a valve shiitable by operation of the pumps and timed to provide a shorter suction stroke at each motor through the pumping stroke thereof, said pumping strokes overlapping each other in respect to duration.

3. In a fuel supply system for an internal combustion engine the combustion of a differentialarea cylinder-and-piston pump, means biasing the piston toward the large end of the cylinder, intermittently operating means for operating said -piston in-the opposite direction against said biasing means, valved inlet and outlet connections to the large end of the cylinder, and a permanently open passage from the small end of the cylinder to the incoming side of the inlet valve, whereby the piston when rapidly retracted by said operating means displaces from the small end of the cylinder a substantial portion of the volume of fuel required to fill the large end thereof.

HARRY F. VICKERS. 

